feat: improved mock server for unit and provider testing #5864

Job	Run time
clippy	1m 5s
docs	2m 11s
check no_std	30s
doctest	2m 45s
feature-checks	5m 27s
feature-propagation	56s
fmt	15s
wasm-unknown	1m 53s
test ubuntu-latest stable --no-default-features	2m 12s
wasm-wasi	2m 57s
test ubuntu-latest stable	2m 19s
test ubuntu-latest stable --all-features	2m 37s
test ubuntu-latest nightly --no-default-features	2m 41s
test ubuntu-latest nightly	2m 45s
test ubuntu-latest nightly --all-features	3m 8s
test ubuntu-latest 1.81 --no-default-features	1m 29s
test ubuntu-latest 1.81	1m 18s
test windows-latest stable --no-default-features	4m 5s
test windows-latest stable	4m 19s
test windows-latest stable --all-features	4m 18s
test windows-latest nightly --no-default-features	5m 8s
test windows-latest nightly	4m 39s
test windows-latest nightly --all-features	4m 30s
test windows-latest 1.81 --no-default-features	2m 58s
test windows-latest 1.81	2m 52s
deny / cargo deny check	20s
ci success	1s
	1h 9m 38s

Provide feedback